Time FreezeRemoves the cast time, but it takes longer to stun enemies.

Notes

Magicka/Stamina Cost is based on a character of Level 50 160. Damage values are based on Max Magicka/Stamina 7958, Max Health 8744, and Weapon/Spell Damage 1037.

Time Stop used on a pair of Goblins. Note the blue aura around them signifying they're stunned.

Time Stop: Cost: [8100 / 8010 / 7920 / 7830]Magicka.
Freeze the passage of time at the target location, gradually reducing the Movement Speed of enemies in the area during the channel before finally stunning them in place for 3 seconds when the channel completes.

Borrowed Time: Cost: [7830 / 7740 / 7650 / 7560]Magicka.
Freeze the passage of time at the target location, gradually reducing the Movement Speed of enemies in the area during the channel before finally stunning them in place for 3 seconds when the channel completes. Enemies that are stunned gain 5000 Heal Absorption for 3 seconds, negating the next 5000 points of healing done.

Time Freeze: Channel Time: Instant, Cost: [7830 / 7740 / 7650 / 7560]Magicka, Duration: 4 seconds.
Freeze the passage of time at the target location, gradually reducing the Movement Speed of enemies in the area over 4 seconds before finally stunning them in place for 3 seconds when the duration completes.

Time Stop reduces the movement speed| of all enemies in the target area before stunning them in place for 3 seconds. The spell has a longish (1.5 second) channel time, which can be negated with the Time Freeze morph (though it takes longer to stun the targets.) Alternatively, the Borrowed Time morph prevents affected targets from being healed for the duration. Note that enemies can move out of the affected area before the stun occurs and will be safe from the worst effects of this, so it's best to distract them into staying within range until the final stun, either by engaging them in melee (yourself or your allies) or knocking them back.